Drain but do not rinse black beans. Mash them with a fork until they are mostly mashed but you still have chunks of black beans. Add the breadcrumbs, onion, egg, and Pace® Salsa Verde Medium. Mix it until everything is combined.
Heat oil in a pan over medium heat. Form 8 equal sized patties roughly the same size as the buns. The black bean burgers will not shrink. Cook for about 5 minutes per side. Remove and keep warm.
In same pan, add a little bit of butter or more oil. Toast buns until lightly browned. Once buns are toasted, crack eggs into the pan and fry them.
While, black bean burgers are cooking, combine the sour cream and Pace® Picante Sauce Medium. Spread on both bun halves. Top with a black bean burger, fried egg, avocado (if using).